Process for making mineral wool fibers from lumps of uncalcined raw

Abstract

A process for making mineral wool fibers having high-temperature stability consisting essentially of: (a) preparing a mixture containing basalt and a quantity of uncalcined raw bauxite sufficient to provide the resulting fibers with an alumina content of at least 18 weight percent, preferably of from 19 to 23 weight percent; (b) heating the mixture to a temperature sufficient to form a substantially homogeneous melt, e.g., in a cupola furnace using coke in a quantity of from about 11 to 25 percent by weight of the mixture; and (c) forming the melt into fibers. The mixture may optionally contain a flux, e.g., limestone and/or dolomite, such as a flux providing a weight ratio of limestone plus dolomite to basalt of less than about 0.6, e.g., 0.1-0.4. The mixture may also contain slag in a weight ratio of slag:basalt of less than about 1.0, more preferably about 0.6. At least about 90% of the uncalcined raw bauxite is of a particle size capable of passing through a 150-mm mesh screen but incapable of passing through a 25-mm mesh screen, more preferably capable of passing through a 125-mm mesh screen but not a 50-mm mesh screen. Preferably, the bauxite has a bound-water content of 10-33 weight percent. The weight ratio of alumina to silica in the fibers is preferably greater than 0.35.